Note: If the listing is being posted to a category that expects an EAN value, but one doesn't exist for the product, the seller must pass in the text that can be found in the ProductDetails.ProductIdentifierUnavailableText field of the GeteBayDetails response. To get the ProductDetails container to return in the GeteBayDetails response, 'ProductDetails' should be included as a DetailName value in the call request.

The issue I'm running into is GeteBayDetails is ignoring the compatibility level header I'm sending and keeps returning a version that predates 'ProductDetails' as an applicable DetailName, so I can't get the ProductIdentifierUnavailableText from it.